The present invention relates to providing a robust error recovery due to data losses incurred during transmission of signals.
A number of techniques exist for reconstructing lost data due to random errors that occur during signal transmission. However, these techniques cannot handle the loss of consecutive packets of data. Consecutive loss of packets of data is described in the art as burst error. Burst errors result in a reconstructed signal with such a degraded quality that it is easily apparent to the end user. Additionally, compression methodologies used to facilitate high speed communications compound the signal degradation caused by burst errors, thus adding to the degradation of the reconstructed signal. An example of burst error loss affecting transmitted and/or stored signals is seen in high definition television (xe2x80x9cHDTVxe2x80x9d) signals and mobile telecommunication applications wherein compression methodologies play an important role.
The advent of HDTV has led to television systems with a much higher resolution than the current standards proposed by the National Television Systems Committee (xe2x80x9cNTSCxe2x80x9d). Proposed HDTV signals are predominantly digital. Accordingly, when a color television signal is converted for digital use it is common that the luminance and chrominance signals are digitized using eight bits. Digital transmission of color television requires a nominal bit rate of two hundred and sixteen megabits per second. The transmission rate is greater for HDTV which would nominally require about 1200 megabits per second. Such high transmission rates are well beyond the bandwidths supported by current wireless standards. Accordingly, an efficient compression methodology is required.
Compression methodologies also play an important role in mobile telecommunication applications. Typically, packets of data are communicated between remote terminals in mobile telecommunication applications. The limited number of transmission channels in mobile communications requires an effective compression methodology prior to the transmission of packets. A number of compression techniques are available to facilitate high transmission rates.
Adaptive Dynamic Range Coding (xe2x80x9cADRCxe2x80x9d) and the discrete cosine transform (xe2x80x9cDCTxe2x80x9d) coding provide image compression techniques known in the art. Both techniques take advantage of the local correlation within an image to achieve a high compression ratio. However, an efficient compression algorithm results in compounded error propagation because errors in an encoded signal are more prominent when subsequently decoded. This error multiplication results in a degraded video image that is readily apparent to the user.
A method for source coding a signal is described. In particular, a signal comprising multiple signal elements is processed. Each signal element is encoded to form a bitstream. The bits within a given bitstream are distributed across different bitstreams. Thus, the parameters describing components of the segment elements are distributed across the different bitstreams. The distributing steps result in error distribution across multiple levels. Therefore, when the distributing steps are reversed by the decoder, a burst transmission error becomes a distributed set of localized losses.
Another method is also described for a multiple level shuffling process. A signal is defined as multiple levels wherein each level comprises a plurality of frames, a plurality of pixels, and a plurality of bits. In one embodiment, shuffling occurs on each level and between levels. Multiple level shuffling causes burst error loss to be distributed across multiple levels thereby facilitating image reconstruction of those areas of the image in which the loss occurred.